In a number of applications, it is desirable to be able to detect IR signals. As such, a variety of IR sensors and coatings have been developed in order to collect and detect IR radiation. Typically, these IR sensors or coatings are designed to detect IR radiation within a specific bandwidth, such as within all or a portion of the near-infrared (NIR) bandwidth defined as 0.75-1.4 μm in wavelength, the short wavelength infrared (SWIR) bandwidth defined as 1.4-3 μm in wavelength, the mid-wavelength infrared (MWIR) bandwidth defined as 3-5 μm in wavelength, or the long-wavelength infrared (LWIR) bandwidth defined as 5-15 μm in wavelength.
Some IR detectors are formed of bulk semiconductor materials. The bulk semiconductor materials absorb infrared radiation at their bandgap. It is desirable in at least some applications to be able to tune the IR detector so as to detect a particular bandwidth of IR radiation. However, the bandwidth of the IR radiation that is absorbed by the bulk semiconductor materials can only be tuned by changing the composition of the semiconductor materials. As such, IR detectors that are formed of bulk semiconductor materials have typically been utilized to detect the NIR and SWIR bandwidths with few IR detectors formed of bulk semiconductor materials being constructed so as to detect IR radiation in the MWIR and/or LWIR bandwidths. However, IR detectors formed of a bulk Hg1-xCdxTe material have been utilized to detect IR radiation throughout the MWIR and LWIR regions as a result of its relatively low bandgap. Unfortunately, Hg1-xCdxTe has a relatively high toxicity level and may be quite expensive, thereby rendering it unsuitable for a number of applications and, in any event, posing at least some challenges during its manufacture and scalability.
As an alternative to the use of bulk semiconductor materials for IR detectors, quantum nanomaterials, such as quantum dots, quantum rods and nano-tetrapods, have been developed that are also capable of absorbing IR radiation. As such, IR detectors may incorporate quantum nanomaterials, i.e., dots, quantum rods or nano-tetrapods, or these materials may be incorporated into paints or other coatings such that the resulting paints or other coatings are sensitive to and capable of absorbing incident IR radiation. Quantum dots, quantum rods and nano-tetrapods have a bandgap that may be tuned by altering the size and morphology of the quantum dots, quantum rods and nano-tetrapods so as to correspondingly alter the region within the IR spectrum to which the quantum nanomaterials are sensitive. However, much of the prior development of nanomaterials such as quantum dots, quantum rods and nano-tetrapods that exhibit quantum confinement has been focused on achieving a relatively high quantum yield (QY) in which the nanomaterial efficiently absorbs and re-emits across the tunable bandgap with the nanomaterial system. Quantum dots, quantum rods and nano-tetrapods are therefore generally configured to absorb visible light, as well as IR radiation in the NIR and SWIR regions and, in some instances, a portion of the MWIR region, but have not generally been capable of absorbing the longer wavelength portion of the MWIR region or the LWIR region of IR radiation.
As such, it may be desirable to provide improved techniques for detecting IR radiation including, for example, improved techniques for detecting IR radiation throughout the MWIR region and into the LWIR region.